MANA （Decentraland）白皮书.pdf

White paperDecentraland is a virtual reality platform powered by the Ethereum blockchain. Users can create, experience, and monetize content and applications. Land in Decentraland is permanently owned by the community, giving them full control over their creations.Users claim ownership of virtual land on a blockchain-based ledger of parcels. Landowners control what content is published to their portion of land, which is identified by a set of cartesian coordinates (x,y). Contents can range from static 3D scenes to interactive systems such as games.Land is a non-fungible, transferrable, scarce digital asset stored in an Ethereum smart contract. It can be acquired by spending an ERC20 token called MANA. MANA can also be used to make in-world purchases of digital goods and services.People are spending increasingly more time in virtual worlds, for both leisure and work1. This occurs predominantly in 2D interfaces such as the web and mobile phones. But a traversable 3D world adds an immersive component as well as adjacency to other content, enabling physical clusters of communities. Unlike other virtual worlds and social networks, Decentraland is not controlled by a centralized organization. There is no single agent with the power to modify the rules of the software, contents of land, economics of the currency, or prevent others from accessing the world.This document lays out the philosophical underpinnings, technical foundations, and economic mechanisms of Decentraland.AbstractEsteban Ordanoesteban@decentraland.orgAriel Meilichari@decentraland.orgYemel Jardiyemel@decentraland.orgManuel Araozmanuel@decentraland.orgA blockchain-based virtual worldDecentralandDecentraland1/141 The State of Mobile, Flurry Analytics Blog. https://flurrymobile.tumblr.com/post/155761509355We would like to thank the following reviewers, whose contributions and feedback made this document possible:Jake Brukhman (Founder, CoinFund)Luis Cuende (Project Lead, Aragon)Simon de la Rouviere (ConsenSys) Diego Doval (Founder of n3xt, previously CTO, Ning)Michael Bosworth (Google)Jesse Walden (Mediachain/Spotify) Chris Burniske (ex ARK Invest)Guillermo Rauch (CEO, Zeit)Joe Urgo (Co-founder, District0x)David Wachsman (Wachsman PR)Jon Choi (Dropbox)Allen HsuDecentraland2/141 Introduction1.1 Rationale1.2 History1.3 A Traversable World1.4 Foundations for an In-world Economy1.5 Use Cases2 Architecture2.1 Consensus Layer2.2 Content Distribution Layer2.3 Real-Time Layer2.4 Payment Channels2.5 Identity System3 Economy3.1 LAND and the MANA Token3.2 Fostering the Network4 Challenge5 Summary4456678991011111212131314Table of ContentsDecentraland3/14Decentraland provides an infrastructure to support a shared virtual world, also known as a metaverse2. It consists of a decentralized ledger for land ownership, a protocol for describing the content of each land parcel, and a peer-to-peer network for user interactions.01 IntroductionThe development of large proprietary platforms, such as Facebook, has allowed hundreds of millions of users to gather, interact, share content, and play games. Their network eﬀects helped cultivate vast online communities and gaming companies. These platforms, controlled by centralized organizations, manage the network’s rules and content flow, while extracting significant revenue from the communities and content creators who drive traﬀic to the platforms. Decentraland aims to establish a network that allows its content creators to own and capture the full value of their contributions.The current team began working on Decentraland in 2015. At the time, the adoption of cryptoassets was still in its infancy, as much of the blockchain-based infrastructure necessary for a consumer-oriented platform was lacking. Since then, the rate of consumer adoption and infrastructure creation has exploded. For instance, by July 2017, Coinbase alone reached 8.4 million user accounts, with half of these added over the past 12 months4. This growth has given rise to a pool of users large enough to fuel the decentralized commerce that will take place in a virtual world like Decentraland. While blockchain infrastructure, spearheaded by Ethereum, is now more widely available, the lack of an eﬀicient method to quickly process micropayments constrains the throughput of network transactions. The maturation of cryptocurrencies as a global, instant, and low cost payment method is still evolving. Payment transactions will need to occur oﬀ-chain to achieve short- to medium-term scalability in blockchain payment networks. Solutions such as Bitcoins Lightning Network5or Ethereums state channels6are on the verge of enabling a fast, global payment system with low fees. 1.1 Rationale01.Introduction 4/142 “The Metaverse”. Wikipedia. https://en.wikipedia.org/wiki/Metaverse3 http://www.kccllc.net/thq/document/12133981307020000000000034 https://www.coinbase.com/about5 “Lightning Apps and the Emerging Developer Ecosystem on LND”. Lightning Network’s Blog. http://lightning.community/software/lnd/lightning/2017/07/05/emerging-lightning-developer-ecosystem/6 “Sprites: Payment Channels that Go Faster than Lightning”. A. Miller, I. Bentov, R. Kumaresan, P. McCorry, 2017. https://arxiv.org/pdf/1702.05812.pdfFigure 1: Stone Age. A visual representation of the blockchain state. Users could mine, transfer, and change the color of pixels they own.More centralized solutions can work today7, although at the expense of operability with other systems, privacy, and standardization. Decentraland is built on the premise that low cost, direct payments between content creators and users will radically change internet commerce.Decentraland began as a proof of concept for allocating ownership of digital real estate to users on a blockchain. This digital real estate was initially implemented as a pixel on an infinite 2D grid, where each pixel contained metadata identifying the owner and describing the pixels color. The experiment was entitled Decentraland’s Stone Age.In late 2016, the team started developing the Bronze Age, a 3D virtual world divided into land parcels. The owner of each parcel was able to associate it with a hash reference to a file, using a modified Bitcoin blockchain. From this reference, users exploring the virtual world could use a Distributed Hash Table (DHT) and BitTorrent to download the file containing the parcel’s content, which defines the models and textures to be displayed at that location.We hosted the first world viewer at decentraland.org/world. Any enthusiast can run a node, download and verify the blockchain, and explore the world by following more advanced instructions8.1.2 History01.Introduction 5/14Figure 2: Bronze Age. Structures created by the community around the Genesis parcel, located at coordinates (0,0)7 “Near-zero fee transactions with hub-and-spoke micropayments”. Peter Todd, bitcoin-development mailing list, December 2014. https://www.mail-archive.com/bitcoin-development@lists.sourceforge.net/msg06576.html8 https://github.com/decentraland/bronzeage-node#run-a-node1.3 A Traversable WorldThe adjacency of land makes Decentraland parcels unique from web domains. New land parcels must be contiguous to existing ones. This adjacency allows for spatial discovery of new content and the creation of districts devoted to a special topic or theme. While each web domain can have an unlimited number of hyperlinks to other content, parcels in Decentraland have a fixed amount of adjacencies. Additionally, the content of adjacent parcels can be seen from a distance. For content creators, the establishment of districts provides access to targeted traﬀic; for end users, it enables discovery of themed experiences. Users can travel through neighborhoods and interact with applications that they stumble upon.This discovery by adjacency is at odds with having infinite land: in that scenario, users would have a hard time finding relevant content by traveling through it. With scarce land, developers can acquire users by purchasing land in high-traﬀic areas. This will allow secondary markets to develop around land ownership and rentals, as is already happening on district0x.io.99 https://blog.district0x.io/decentraland-districts-40b9ada0431bThe next version of Decentraland, the Iron Age, will create a social experience with an economy driven by the existing layers of land ownership and content distribution. In the Iron Age, developers will be able to create applications on top of Decentraland, distribute them to other users, and monetize them.The Iron Age will implement peer-to-peer communications, a scripting system to enable interactive content, and a system of fast cryptocurrency payments for in-world transactions. A communication layer is essential for social experiences, providing positioning, postures, voice chat, and more; Decentraland achieves this with a P2P network. The scripting system is the tool that landowners will use to describe the behavior and interactions of 3D objects, sound, and applications running on land parcels. Finally, a payment system with low fees is key to developing an economy in the quick environment of a virtual world.01.Introduction 6/14Decentraland’s value proposition to application developers is that they can fully capitalize on the economic interactions between their applications and users. To allow those economic interactions, the platform must allow three things to be traded: currency, goods, and services.Decentraland will integrate a core system that allows global, instant, and cost-eﬀective payments between any two users on the internet. Cryptocurrencies allow for trustless payment channels to be established between parties, with low-trust hub-and-spoke systems already possible.1.4 Foundations for an In-world Economy10 “Rare Pepe”. Fred Wilson. https://avc.com/2017/05/rare-pepe/01.Introduction 7/14For services to be provided on Decentraland, we are developing a scripting system that enables developers to program the interactions between users and applications. This scripting system runs exclusively on the client side but allows for diﬀerent data flow models: from mere local eﬀects and traditional client-server architectures, to P2P interactions based on state channels. Developers programming in it will benefit from the availability of fast, cheap micropayments, provably fair games, decentralized storage, and other features enabled by the advent of cryptographic techniques using blockchain-based smart contracts.To foster the exchange of virtual goods, economic incentives must be in place to ensure the continued creation and distribution of avatars, items, and scripts. Because static content can be arbitrarily copied, the user experience should empower social agreements that recognize original creations. By implementing an identity system to establish authorship, users will be able to track and verify an author’s consent through cryptographic signatures. These experiments are already happening, as in the case of Rare Pepes10.ApplicationsThe Decentraland scripting language will allow the development of applications, games, gambling, and dynamic 3D scenes. This scripting language will be designed to handle a wide range of capabilities, including creating objects, loading textures, handling physics, encoding user interactions, sounds, payments, and external calls, among others.Content CurationUsers in Decentraland will gather around neighborhoods of shared interest. Being located near high-traﬀic hubs will drive users to the landowners’ content.AdvertisingBrands may advertise using billboards near, or in, high-traﬀic land parcels to promote their products, services, and events. Some neighborhoods may become virtual versions of Times Square in New York City. Additionally, brands may position products and create shared experiences to engage with their audience.Digital CollectiblesWe expect users to publish, distribute, and collect rare digital assets issued on the blockchain by their creators. Just as it occurs today in other virtual worlds or through online forums, these digital assets will be traded inside this world through the scripting system and be backed by the aforementioned naming system.1.5 Use Cases02.Architecture 8/14SocialGroups that currently gather in online forums, chat groups, or even other centralized multiplayer games could port their communities into Decentraland. Oﬀline communities could also find in Decentraland a space to gather.Other use casesThere are no technical specifications to what could be built in Decentraland. Therefore, other use cases could emerge, such as training and professional development, education, therapy, 3D design, and virtual tourism, among others.The Decentraland protocol is comprised of three layers:02 Architecture1) Consensus layer: Track land ownership and its content.2) Land content layer:Download assets using a decentralized distribution system.3) Real-time layer:Enable users’ world viewers to connect to each other.Land ownership is established at the consensus layer, where land content is referenced through a hash of the file’s content. From this reference the content can be downloaded from BitTorrent or IPFS. The downloaded file contains a description of objects, textures, sounds, and other elements needed to render the scene. It also contains the URL of a rendezvous server to coordinate connections between P2P users that are exploring the tile simultaneously. Figure 3 shows a diagram of the steps the Decentraland clients execute to provide the experience of a shared virtual world in a decentralized way.Figure 3: The Decentraland protocol for simultaneous users in a decentralized virtual world.11 https://ipfs.io12 https://filecoin.io/02.Architecture 9/14Decentraland will use an Ethereum smart contract to maintain a ledger of ownership for land parcels in the virtual world. We call these non-fungible digital assets LAND: each LAND has unique (x, y) coordinates, an owner, and a reference to the content description file, which encodes what the landowner wants to serve there. Decentraland clients will connect to the Ethereum network to fetch updates to the state of the LAND smart contract.LAND is bought by burning MANA, a fungible ERC20 token of fixed supply. This token serves as a proxy for the cost of claiming a new parcel. The LAND contract uses a burn function to destroy MANA and create a new entry in the LAND registry. New parcels need to be adjacent to a non-empty parcel.2.1 Consensus LayerDecentraland uses a decentralized storage system to distribute the content needed to render the world. For each parcel that needs to be rendered, a reference to a file with the description of the parcel’s content is retrieved from the smart contract. The current solution uses the battle-tested BitTorrent and Kademlia DHT networks by storing a magnet link for each parcel. However, the Inter-Planetary File System (IPFS)11provides a compelling alternative as